Bioassay on peach seedlings GF305 and immunoenzymatic assay (ELISA) for the detection of fruit tree viruses | Intérêts comparés de l’indexage biologique sur semis de pêcher GF 305 et du diagnostic immunoenzymatique ELISA pour la détection de virus des espèces fruitières

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Francés. The peach seedling GF 305 is an indicator plant commonly used in the greenhouse for detecting several fruit tree viruses ; it is well known for its sensitivity and its potentiality to detect many virus and virus-like diseases. Comparative indexing of 534 stone fruit tree samples has been carried out on GF 305 and by ELISA for the detection of apple chlorotic leaf spot (CLSV) and two viruses of the ILAR virus group, Prunus necrotic ring spot (NRSV) and prune dwarf (PDV). Number of infected samples was higher in ELISA than with GF 305 (276/238). Nevertheless the correlation was not perfect. The ELISA technique seems to be more reliable : CLSV and viruses of the ILAR virus group are identified by ELISA in respectively, 68 and 54 samples which do not induce any symptom on GF 305. But conversely, in the search for CLSV, 64 samples which induce symptoms on GF 305 do not give any reaction in ELISA : this could mean some confusion of symptoms of the GF 305 or reflect the existence of particular strains. In another work we demonstrate that most known NRSV or PDV strains can be detected by ELISA in the conditions used for the present investigations. Apple mosaic virus, a virus that we have frequently detected in stone fruit trees, especially in almond trees, was not investigated with ELISA and could be responsible for symptom expression on GF 305. This paper shows that neither GF 305 nor ELISA are able to detect all the cases of infection but ELISA appears clearly superior to the GF 305 bioassay in a routine indexing scheme, especially for recontamination investigations.